International Workshop on Accelerator AlignmentDESY, Hamburg Germany

Graphical and Numeric Measurement Station

Uncertainty Characterization

Scott SandwithNew River Kinematicsscott@kinematics.com

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Introduction• Network Adjustment (Inputs v. Outputs)• Compute and report instrument (station) position

variation during Monte Carlo– Save each station position during Monte Carlo computation– Compute std dev of each position/orientation parameter based

on the samples – Report station variations

• Instrument Position/Orientation Uncertainty Report• Conclusions

Communicating Uncertainty Estimates• Understanding and communicating

reliable measurement uncertainty• In many cases measurement

process uncertainty is difficult to control – Geometry constraints within facility

• Methods to characterize and communicate specific influences and dependences are key tools for alignment teams

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Accelerator Surveys• Inputs

– Instruments (Types Stations, Performance, and Environment)– Control/Constraints (Instrument, Levels, Scale Bar(s) Distance)– Point/Observation Network– Reflector and Targeting Offsets, Errors (e.g., hidden pts, vector

bars)• Outputs

– Network Adjustment– Uncertainty Analysis – Study – Confidence

• Points• Stations• Geometry

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Why Instrument Uncertainties?• Point uncertainties are primary output of

interest• To influence pt uncertainty understanding

instrument/station uncertainty – Ux, Uy, Uz, URx, URy, URz, U_TA

is a key element to influence and control alignment network uncertainty

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Objective Uncertainty Feedback• Objectively characterizing and visualizing

each stations position and orientation uncertainty in context of network is helpful

• Understanding influences and dependence that station position and precision plays enables alignment teams to make objective choices on effective optimize station performance and position(s).

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Case Studies• Individual station uncertainty within network

results are presented both graphically and numerically

• Evaluation and graphical results show net differences in how measurement network from a station influences component alignment characterization

• Outcome Choices in which sensors are used and how their position(s) within network influence alignment fidelity

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Simple Example

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Open Network Effects

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Uncertainty Comparison

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Open Network Fixed Total Station

Closed Network Fixed Total Station

Closed Network Free Network Adjustment

Compare: Open/Closed Survey

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Closed Survey FreeNet

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Accelerator Network

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Free Network Instrument Uncertainty

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Comparison between Fixed and Freenet

International Workshop on Accelerator AlignmentDESY Hamburg Germany

Instrument/Station Uncertainty Conclusions• Measure of how encompassing pt network is

about each station • Larger instrument uncertainty results if the pt

network is within a narrow field of view• When common pt network is uniformly

distributed instrument uncertainty looks worse but will provide more conservative estimates of performance

• Using variation of station position during Monte Carlo provides a reasonable measure of the rigor of the network

International Workshop on Accelerator AlignmentDESY Hamburg Germany